Use of recycled plastics for structural building forms

ABSTRACT

Modular plastic structural composites having a web section disposed along a horizontal axis and at least one flange section disposed along a horizontal axis parallel thereto and integrally molded to engage the top or bottom surface of the web section, wherein said composite is formed from a mixture of (A) high density polyolefin and (B) a thermoplastic-coated fiber material, poly-styrene, or a combination thereof. Composites molded in the form of I-Beams and bridges constructed therefrom are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/870,277, filed Aug. 27, 2010, now U.S. Pat. No. 7,996,945, which is adivisional of U.S. patent application Ser. No. 10/563,883, filed on June8, 2006, and issuing as U.S. Pat. No. 7,795,329, which is the NationalStage Entry under 35 U.S.C. §371 of International Patent ApplicationSerial No. PCT/US03/22893, filed on Jul. 21, 2003, which claims thebenefit of U.S. Provisional Patent Application Ser. No. 60/486,205,filed on Jul. 8, 2003. The disclosures of all of these applications areincorporated herein by reference.

FIELD OF THE INVENTION

This invention pertains to new building forms made ofdegradation-resistant composites; structures produced from such novelforms; and related methods of producing and using such forms andstructures.

BACKGROUND OF THE INVENTION

There presently are over 500,000 wooden vehicular bridges in the UnitedStates assembled from chemically treated lumber. An estimated fortypercent of them are in need of repair or replacement.

There are several types of chemically treated lumber such as creosotedlumber and pressure treated lumber. These materials are relativelyinexpensive to make and use, and they are just as versatile as any otherform of wood. They also have enhanced resistance to microbial and tofungal degradation and to water.

However, the increasing popularity of chemically treated lumber has somenegative repercussions that are just now being realized. Chemicallytreating lumber takes a perfectly useable, recyclable, renewableresource and renders it toxic. For example “pressure treated” or “CCA”lumber is treated with very poisonous chromated copper arsenic andcannot be burned. While CCA lumber can be buried, the leaching of toxicchemicals makes such disposal strategies undesirable. The disposal ofcreosoted lumber requires the use of special incinerators. Thesematerials are becoming far more difficult and expensive to dispose ofthan to use. However, because of the long useful life of thesematerials, the economic and environmental impact of chemically treatedlumber is just beginning to be felt.

Structural recycled plastic lumber represents a possible alternative tochemically treated lumber. U.S. Pat. Nos. 6,191,228, 5,951,940,5,916,932, 5,789,477, and 5,298,214 disclose structural recycled plasticlumber composites made from post-consumer and post-industrial plastics,in which polyolefins are blended with polystyrene or a thermoplasticcoated fiber material such as fiberglass. These structural compositespresently enjoy commercial success as replacements for creosotedrailroad ties and other rectangular cross-sectioned materials. Themarket has otherwise been limited for structural recycled plasticlumber, because it is significantly more expensive than treated woodenbeams on an installed cost basis, despite the use of recycled wasteplastics.

This significant cost difference became more evident in the constructionof bridge structures in which pressure-treated wooden beams werereplaced with structural recycled plastic lumber composite beams. Whileas strong as CCA treated wood, the recycled plastic composite beams werenot as stiff, and tended to sag, or “creep.” It was possible tocompensate for this by increasing beam dimensions and using more beamsof rectangular cross-section. However, this just added to the alreadyincreased cost for materials and construction in comparison to treatedlumber.

Structural beams that do not “creep” can also be prepared fromengineering resins such as polycarbonates or ABS. However, these areeven more costly than the structural composites made from recycledplastics. There remains a need for structural materials based onrecycled plastics that are more cost-competitive with treated lumber onan installed cost basis.

BRIEF SUMMARY OF THE INVENTION

It has now been discovered that the immiscible polymer blends of U.S.Pat. Nos. 6,191,228, 5,951,940, 5,916,932, 5,789,477, and 5,298,214 canbe formed into structural shapes that are more cost-efficient thantraditional recycled plastic structural beams with rectangularcross-sections. The structural shapes according to the present inventionare molded as a single integrally-formed article and include modularforms such as I-Beams, T-Beams, C-Beams, and the like, in which one ormore horizontal flanges engage an axially disposed body known in the artof I-Beams as a web. The reduced cross-sectional area of such formsrepresents a significant cost savings in terms of material usage withoutsacrificing mechanical properties. Additional cost saving are obtainedthrough modular construction techniques permitted by the use of suchforms.

Therefore, according to one aspect of the present invention, a modularplastic structural composite is provided having web section disposedalong a horizontal axis and at least one flange section disposed along ahorizontal axis parallel thereto and integrally molded to engage the topor bottom surface of the web section, wherein the composite is 5 formedfrom a mixture of (A) high density polyolefin and (B) athermoplastic-coated fiber material, polystyrene, or a combinationthereof. The high-density polyolefin is preferably high-densitypolyethylene (HDPE). The thermoplastic-coated fiber material ispreferably a thermoplastic-coated carbon, or glass fibers such asfiberglass.

The flange dimensions relative to the dimensions of the web sectioncannot be so great to result in buckling of the flange sections upon theapplication of a load. Preferably, the vertical dimension (thickness) ofthe flange section is about one-tenth to about one-half the size of thevertical dimension of the web section without any flange section(s) andthe width dimension of the entire flange section measured perpendicularto the horizontal axis of the flange section is about two to about tentimes the size of the width dimension measured perpendicular to thehorizontal axis of the web section.

Other efficient structural shapes according to the present inventioninclude tongue-in-groove shaped boards that form interlockingassemblies. It has been discovered that interlocking assemblies reducethe required board thickness because of the manner in which the assemblydistributes loads between the interlocked boards. This also represents asignificant cost savings in terms of material usage without sacrificingmechanical properties, with additional cost savings also obtainedthrough the modular construction techniques these forms permit.

Therefore, according to another aspect of the present invention, anessentially planar modular plastic structural composite is providedhaving a grooved side and an integrally molded tongue-forming side, eachperpendicular to the plane of the composite, in which the composite isformed from a mixture of (A) high-density polyolefin and (B) athermoplastic-coated fiber material, polystyrene, or a combinationthereof, wherein the grooved side defines a groove and thetongue-forming side is dimensioned to interlockingly engage a groovehaving the dimensions of the groove defined by the grooved side, and thegrooved side and tongue-forming side are dimensioned so that a pluralityof the essentially planar modular plastic structural composites may beinterlockingly assembled to distribute a load received by one assemblymember among other assembly members.

Preferred planar modular plastic structural composites have at least onepair of parallel opposing grooved and tongue-forming sides, definingtherebetween a width or length dimension of the composite. Preferredcomposites also have board-like dimensions in which the length dimensionis a matter of design choice and the width dimension is between abouttwo and about ten times the size of the height, or thickness, dimensionof the composite.

The modular plastic structural composites have utility in theconstruction of load-bearing assemblies such as bridges. Therefore,according to yet another aspect of the present invention, a bridge isprovided, constructed from the I-Beams of the present invention, havingat least two pier-supported parallel rows of larger first I-beams, and aplurality of smaller second I-beams disposed parallel to one another andfastened perpendicular to and between two rows of the larger firstI-Beams, wherein the top and bottom surfaces of the second I-Beamflanges are dimensioned to nest within the opening defined by the topand bottom flanges of the first I-Beams.

The distance between the rows of first I-Beams and the rows of secondI-Beams will depend upon factors such as the flange and web dimensions,the plastic components of the composite and the load to be supported bythe bridge. Furthermore, whether the horizontally disposed axes of thefirst or second I-Beams extend in the direction of travel on the bridgeis a matter of design choice, which may in whole or in part depend uponthe aforementioned factors.

Because the second I-Beams are nested within the opening defined by thetop and bottom flanges of the first I-Beams, the top surfaces of thesecond I-Beams are recessed below the top surfaces of the first I-Beamsby a distance that is at least the thickness dimension of the top flangeof the first I-Beam. Bridges constructed according to this aspect of thepresent invention will therefore further include a deck surface fastenedto the first or second I-Beams. Preferred deck surfaces are dimensionedto fit between the top flanges of the parallel rows of the firstI-beams. Even more preferred deck surfaces have a thickness dimensionselected to provide the deck surface with a top surface that isessentially flush with the top surfaces of the parallel rows of firstI-Beams. Other preferred deck surfaces are formed from the essentiallyplanar modular plastic structural composites of the present inventionhaving interlocking grooved and tongue-forming sides.

The modular components of the present invention permit the constructionof load-bearing assemblies with fewer required fasteners, reducing theinitial bridge cost, as well as the long-term cost of maintaining andreplacing these corrosion-prone components. The plastic compositematerial also outlasts treated wood and requires significantly lessmaintenance than wood over its lifetime, further contributing to costsavings.

The foregoing and other objects, features and advantages of the presentinvention are more readily apparent from the detailed description of thepreferred embodiments set forth below taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a cross-sectional view of an I-Beam according to thepresent invention;

FIG. 2 is a side-view of the I-Beam of FIG. 1, perpendicular to thecross-sectional view;

FIG. 3 depicts a cross-sectional view of a C-Beam according to thepresent invention;

FIG. 4 is a side view of the C-Beam of FIG. 3, perpendicular to thecross-sectional view;

FIG. 5 depicts a cross-sectional view of a T-Beam according to thepresent invention;

FIG. 6 is a bottom view of the T-Bean of FIG. 5;

FIG. 7 depicts a cross-sectional view of tongue and groove deckingpanels according to the present invention;

FIG. 8 depicts a side view of a bridge according to the presentinvention assembled from the I-Beams of the present invention;

FIG. 9A is a top cutaway view of the bridge of FIG. 8, and FIG. 9B is atop cutaway view of the bridge of FIG. 8; and

FIG. 10 is a top cutaway view depicting the perpendicular fastening of asmaller I-Beam according to present invention to a larger I-Beamaccording to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The modular plastic structural composites of the present invention areprepared using the co-continuous polymer blend technology disclosed byU.S. Pat. Nos. 5,298,214 and 6,191,228 for blends of a high-densitypolyolefin and polystyrene and by U.S. Pat. No. 5,916,932 for blends ofa high-density polyolefin and thermoplastic-coated fiber materials. Thedisclosures of all three patents are incorporated herein by reference.

As disclosed in U.S. Pat. No. 6,191,228 composite materials may beemployed containing from about 20 to about 50 wt % of a polystyrenecomponent containing at least about 90 wt % polystyrene and from about50 to about 80 wt % of a high-density polyolefin component containing atleast about 75 wt % high-density polyethylene (HDPE). Compositematerials containing about 25 to about 40 wt % of a polystyrenecomponent are preferred, and composite materials containing about 30 toabout wt % of a polystyrene component are even more preferred.Polyolefin components containing at least about 80 wt % HDPE arepreferred, and an HDPE content of at least about 90 wt % is even morepreferred.

According to the process disclosed by U.S. Pat. No. 5,916,932 thiscomposite may be further blended with thermoplastic-coated fibers havinga minimum length of 0.1 mm so that the finished product contains fromabout 10 to about 80 wt % of the thermoplastic-coated fibers. U.S. Pat.No. 5,916,932 discloses composite materials containing from about 20 toabout 90 wt % of a polymer component that is at least 80 wt % HDPE andfrom about 10 to about 80 wt % of thermoplastic-coated fibers.

The polyolefin-polystyrene composite materials suitable for use with thepresent invention exhibit a compression modulus of at least 170,000 psi.and a compression strength of at least 2500 psi. Preferredpolyolefin-polystyrene composite materials exhibit a compression modulusof at least 185,000 psi and a compression strength of at least 3000 psi.More preferred polyolefin-polystyrene composite materials exhibit acompression modulus of at least 200,000 psi and a compression strengthof at least 3500 psi.

Composite materials containing thermoplastic-coated fibers according tothe present invention exhibit a compression modulus of at least 350,000psi. The compression modulus exhibited by preferred fiber-containingmaterials is at least 400,000 psi. The composite materials containingthermoplastic-coated fibers exhibit a compression strength of at least4000 psi. The compression strength exhibited by preferredfiber-containing materials is at least 5000 psi.

A cross-sectional view of an I-Beam 10 according to the presentinvention is depicted in FIG. 1, with a side view of the same I-Beamshown in FIG. 2. The I-beam has a traditional structure consisting ofmiddle “web” or “body” section 20, an upper flange 30, and a lowerflange 40. The flange sections include a protruding section 50 thatextends beyond the width of the web 20. The face of the web 60 forms astructure that can engage other structures (e.g., smaller beams), asdescribed further below. The width A of the flange sections issignificantly wider than the width B of the web section. The height C ofthe flange sections is smaller than the height of the web sections.Despite the thin height of the flange section and the narrow width ofthe web section, the I-Beam is capable of supporting heavy structuresand can be used in load-bearing structures, such as bridges and thelike.

A cross-sectional view of a C-Beam 12 according to the present inventionis depicted in FIG. 3, with a side view of the same C-Beam shown in FIG.4. The C-beam also has a middle web section 20, an upper flange 30, anda lower flange 40. The flange sections also include a protruding section50 that extends beyond the width of the web 20. The face of the web 60also forms a structure that can engage other structures (e.g., smallerbeams), as described further below.

A cross-sectional view of a T-Beam 15 according to the present inventionis depicted in FIG. 5, with a bottom view of the same T-Beam shown inFIG. 6. The T-beam has a structure consisting of middle web section 20and an upper flange 30, but no lower flange. The flange section alsoincludes a protruding section 50 that extends beyond the width of theweb 20. The face of the web 60 also forms a structure that can engageother structures (e.g., smaller beams), as described further below.

FIG. 7 shows assembled tongue-and-groove decking panels 100 and 150.Panel 100 includes an end 110 having a tongue-shaped member 120 and anopposite end 130 defining a groove 140. Panel 150 includes an end 160having a tongue-shaped member 170 and an opposite end 180 defining agroove 190. Tongue-shaped member 120 of panel 100 is depictedinterlockingly engaging the groove 190 of panel 150. The groove 140 ofpanel 100 is also capable of interlockingly engaging a tongue-shapedmember of another panel. Likewise, the tongue-shaped member 170 of panel150 is capable of engaging a groove of another panel. Flat top 125 ofpanel 100 and flat top 175 of panel 150 can serve as a load-bearingsurface or barrier when such panels are assembled into a structure.

FIG. 8 illustrates a side view and FIG. 9 a top partial cutaway view ofa portion of a vehicular bridge 200 assembled from the above-describedbuilding forms. In the bridge structure, ends 211 and 212 of respectivelarger I-beam rails 213 and 214 are secured to respective pilings 216and 217 by fasteners (not shown). The opposite respective I-Beam ends220 and 221 are similarly secured to respective pilings 223 and 224.Ends 225, 226 and 227 of smaller joist I-beams 228, 229 and 230 arefastened to the face 260 of I-Beam 213, with respective opposing ends231, 232 and 233 of the three smaller I-Beams fastened to the face 261of I-Beam 214. Similarly, ends 234, 235 and 236 of smaller joist I-beams237, 238 and 239 are fastened to the face 262 of I-Beam 214.

FIG. 10 is a top cutaway view depicting the fastening of end 225 ofsmaller joist I-Beam 228 to the face 260 of larger I-Beam 213 usingL-shaped brackets 243 and 244 and fasteners 245, 246, 247 and 248.Bracket 243 and fasteners 245 and 246 fastening the end 225 of I-Beam228 to face 260 of I-Beam 213 is also shown in FIG. 8. FIG. 8 also showsbracket 247 and fasteners 248 and 249 fastening end 231 of I-Beam 228 toface 261 of I-Beam 214.

FIGS. 8 and 9 also show bridge deck 270 formed from interlocking panels271 and 272 in which tongue 274 of panel 271 interlockingly engagesgroove 275 of panel 272. Tongue 276 of panel 272 interlockingly engagesgroove 277, and so forth. The respective top surfaces 279 and 280 ofpanels 271 and 272 comprise the surface 290 of bridge deck 270.

Suitable fasteners are essentially conventional and include, withoutlimitation, nails, screws, spikes, bolts, and the like.

The molding processes disclosed in U.S. Pat. Nos. 5,298,214, 5,916,932and 6,191,228 may be employed to form the modular plastic structuralcomposite shapes of the present invention. However, because articles arebeing formed having an irregular cross section in comparison to thebeams having rectangular cross-sections that were previously molded, thecomposite blends are preferably extruded into molds from the extruderunder force, for example from about 900 to about 1200 psi, to solidlypack the molds and prevent void formation. Likewise, it may be necessaryto apply force along the horizontal beam axis, for example using ahydraulic cylinder extending the length of the horizontal axis, toremove cooled modular shapes from their molds.

Composite I-Beams of polyolefin and polystyrene according to the presentinvention having a 61 square-inch cross-sectional area exhibit a Momentof Inertia of 900 in⁴. Poly-olefin-polystyrene composite I-Beamsaccording to the present invention having a 119 square-inchcross-sectional area exhibit a Moment of Inertia of 4628 in⁴. Thisrepresents the largest Moment of Inertia ever produced by anythermoplastic material for any structure, and compares to Moments ofInertial measured between 257 and 425 in⁴ for rectangular cross-sectionwooden beams having a 63 square-inch cross-sectional area and Moments ofInertial measured between 144 and 256 in⁴ for rectangular cross-sectionwooden beams having a 48 square-inch cross-sectional area. The endresult is that a polyolefin-polystyrene composite bridge that would haveweighed 120,000 pounds for the required load rating if prepared fromrectangular cross-section composite materials, weighs just 30,000 poundsinstead when prepared from the I-Beams of the present invention.

The modular plastic structural composites of the present invention thusrepresent the most cost-effective non-degradable structural materialsprepared to date having good mechanical properties. The presentinvention makes possible the preparation of sub-structures with givenload ratings from quantities of materials reduced to levels heretoforeunknown.

The foregoing description of the preferred embodiment should be taken asillustrating, rather than as limiting, the present invention as definedby the claims. As would be readily appreciated, numerous variations andcombinations of the features set forth above can be utilized withoutdeparting from the present invention as set forth in the claims. Suchvariations are not regarded as a departure from the spirit and scope ofthe invention, and all such variations are intended to be includedwithin the scope of the following claims.

What is claimed is:
 1. A planar modular plastic structural compositecomprising at least one pair of a grooved side and an integrally moldedtongue-forming side positioned parallel opposing to each other, definingtherebetween a width or length dimension of the composite, wherein saidwidth dimension is between about two and about ten times the size of theheight (thickness) dimension of the composite, each side perpendicularto the plane of the composite, in which the composite is formed from aco-continuous immiscible polymer blend consisting essentially of ahigh-density polyolefin and a thermoplastic polymer-coated fibermaterial or a thermoplastic polymer having fiber material embeddedtherein, wherein the grooved side defines a groove comprising a topsurface, a side surface, and a bottom surface and the tongue-formingside is dimensioned to possess a tongue-shaped member comprising a topsurface, a side surface, and a bottom surface that interlockingly engagea groove having the dimensions of the groove defined by the groovedside, and the grooved side and tongue-forming side are dimensioned sothat the top surface, the side surface, and the bottom surface of thetongue-shaped member directly contact each corresponding top surface,side surface, and bottom surface of the groove and a plurality of theessentially planar modular plastic structural composites may beinterlockingly assembled to distribute a load received by one assemblymember among other assembly members.
 2. The modular plastic composite ofclaim 1, wherein said composite comprises from about 20 to about 90 wt %of a polymer component that is at least 80 wt % HDPE and from about 10to about 80 wt % of thermoplastic-coated fibers.